Refrigeration apparatus for operation under low head pressures



May 19, 1964 R. w. JOHNSON 3,133,426 REFRIGERATION APPARATUS FOR OPERATIGN UNDER LOW HEAD PRESSURES Filed Oct. 4, 1962 \Z/ FIG. I

INVENTOR. ROBERT W. JOHNSON.

- ATTORNEY.

United States Patent Ofi ice 3,133,426 Patented May 19, 1964 3,133,426 REFRIGERATIGN APPARATUS FOR QPERATION UNDER 18W HEAD PREdSURES Robert W. .iohnson, De Witt, N.Y., assignor to Carrier Corporation, Syracuse, N.Y., a corporation of Delaware Filed Oct. 4, 1962, Ser. No. 228,431 6 Claims. (Cl. 62-196) The present invention relates to an improved refrigeratlon system and more particularly to a refrigeration system which will provide efiicient operation under low ambient temperature conditions which produce low condenser or head pressures.

A conventional refrigeration system includes a closed circuit having a compressor, condenser, expansion means and evaporator in series. Refrigerant is pumped by the compressor to the condenser wherein the heat of compression is removed by heat exchange between the condensed gases in the condenser and the ambient air. However, under normal operating conditions within a predetermined range of ambient temperatures, the refrigerant in the condenser, after said cooling has occurred, remains at a sufiiciently high pressure to force the liquefied refrigerant through the expansion means to an evaporator. In the evaporator, the liquid refrigerant is placed in heat exchange relation with a medium to be treated thus absorbing heat from the area in which the evaporator is located and changing the refrigerant phase from a liquid to a gas. However, when the ambient temperature of the air, which is utilized to condense the compressed gases in the condenser, drops below the predetermined range of temperatures, the gases in the condenser condense to a relatively great extent and therefore a condition arises Where there is insufficient pressure in the condenser to effect proper flow of the refrigerant through the expansion means leading to the evaporator.

In the past, one way of solving the foregoing problem was by causing liquid refrigerant to hang up in the condenser to thereby effectively decrease the condenser area by blocking a portion thereof. The raising of the condenser pressure in this manner provided sufficient pressure in the condenser so that satisfactory operation of the expansion means was obtained. One Way of effecting the above described liquid hang up was by passing hot gases from the compressor directly into the line leading from the condenser to the expansion means thereby preventing a certain amount of the liquid refrigerant in the condenser from flowing therefrom. If too much liquid refrigerant was caused to remain in the condenser as a result of the foregoing procedure, the outlet of the compressor was blocked to too great a degree and the maximum permissible compressor pressure would be exceeded with the attendant cycling of the compressor to an off condition. After the compressor pressure was relieved, the compressor would cycle to an on condition. The foregoing occurred especially during initiation of the operation of the refrigeration system and caused objectionable cycling as the compressor was caused to alternately runand shut off. The present invention is concerned with the provision of an improved refrigeration system which eliminates these disadvantages of prior constructions.

The primary object of the present invention is to provide an improved refrigeration system which is capable of causing the condenser or head pressure to be raised under low ambient temperature condenser cooling conditions while obviating the tendency for compressor. cycling.

An object of the present invention is to provide an improved refrigeration system wherein a single component thereof acts both to cause liquid refrigerant to hang up in the condenser to thereby raise the condenser pressure under low ambient condenser cooling conditions and also acts to induce a portion of the condensed refrigerant from the condenser when the compressor pressure tends to exceed a predetermined maximum value thereby preventing cycling of said compressor. Other objects and advantages of the present invention will readily be perceived hereafter.

In accordance with the present invention, a conventional refrigeration circuit is provided having a compressor, a condenser, expansion means and an evaporator coupled in a series circuit relationship. In addition, an ejector is provided. The inlet to the ejector is from the outlet of the condenser. The nozzle of the ejector is in communication with the outlet of the compressor through a suitable conduit. A control valve is placed in this con duit and this valve is controlled by the pressure in the outlet of the ejector. When the refrigeration system is operating within a given range of ambient condenser cooling temperatures so that the condenser pressure is above a predetermined minimum value sufficient to cause proper flow of refrigerant through the refrigerant circuit, the pressure at the outlet of the ejector will be such to cause said valve to be closed and thereby prevent flow of hot gases from the compressor to the ejector nozzle. Under the foregoing circumstances, the refrigeration system will operate in its normal conventional manner and the ejector will merely act as a conduit for transmitting liquid refrigerant from the condenser to the expansion means. However, in the event that the ambient condenser cooling temperature causes the condenser pressure to fall below a predetermined value, the valve means between the compressor outlet and the ejector nozzle will open, in response to the low pressure existing at the outlet of the ejector, to permit hot gases from the compressor to flow through the ejector nozzle, and these hot gases will mix with liquid refrigerant coming from said condenser in the ejector. This mixing of gaseous and liquid refrigerant tends to retard flow of liquid refrigerant from the condenser, in effect, causing liquid refrigerant to hang up in the condenser thereby raising the condenser pressure to a value which is sufficient for proper operation of the expansion means. Under these circumstances, the ejector will merely act as a mixer.

When the quantity of liquid refrigerant in the condenser has increased to a point adequate to cause the condenser pressure to meet the refrigeration requirements, the pressure of gases leaving the compressor will tend to rise. Since these gases are in communication with the ejector nozzle, an increased flow of gases will be experienced through the ejector nozzle and the ejector may cease serving as a mixing chamber for causing refrigerant hang up in the condenser, and commerce acting as an ejector to exhaust liquid refrigerant from the condenser thereby reducing the pressure of gases leaving the compressor.

The combined mixing and ejecting function of the ejector causes the refrigeration system to operate efficiently by keeping the condenser pressure above the predetermined value required for proper system operation and by preventing the compressor pressure from exceeding a maximum permissible value, obviating cycling of the compressor, especially at system start-up when cycling is most prevalent. The present invention will be more fully understood when the following portions of the specification are read in conjunction with the accompanying drawing.

The attached drawing illustrates preferred embodiments of the invention, in which: 7

FIGURE 1 is a diagrammatic view of a refrigeration system employing the present invention; and

FIGURE 2 is a diagrammatic view of a modified form of the invention shown in FIGURE 1.

Referring to the drawing, a compressor 10 is shown which is in communication with condenser 11 through conduit 12. The gaseous refrigerant which is compressed by compressor it) is condensed in condenser 11 because of the heat exchange between the gases in condenser 11 and the flow of ambient air effected by fan 13 across the outer surfaces of condenser 11. The condensed liquid refrigerant thereafter passes through conduit 14 and into inlet 15 of ejector 1e and thereafter flows into receiver 17. From receiver 17, the liquid refrigerant fiows to thermal expansion valve 18 through conduit 19.

Thermal expansion valve 18, as is well known in the art, has a thermal sensing bulb 2t in contact with the suction line 2-3 of the system, bulb 2% being in communication with thermal expansion valve 18 through capillary 22. The amount of refrigerant passing through thermal expansion valve 13 is determined by the temperature in suction line 23 as reflected by bulb 26). It will be appreciated that when the ambient air temperature is within a predetermined range of values, there will be sufficient pressure of refrigerant in condenser 1.1 to force refrigerant through the thermal expansion valve 18.

After the refrigerant leaves thermal expansion valve 18, it flows into evaporator 21 wherein the refrigerant is placed in heat exchange relation with a medium to be treated thus absorbing heat therefrom and changing the refrigerant from a liquid state to a gaseous state. A fan 24- is associated with evaporator 21 to pass air from the area to be cooled thereover. The gaseous refrigerant leaving evaporator 21 returns to the inlet of compressor 10 via conduit 23.

It will be understood that suitable wiring arrangements, conventional in the art, are provided for the operation of fans 13 and 24, these wiring relationships being omitted from the drawing inasmuch as they form no part of the present invention.

As long as the ambient air temperature utilized for cooling condenser 11 is within a predetermined range of values, the refrigeration system will operate in the above described manner. However, there are times when the ambient air temperature falls below the predetermined range of values and causes the pressure within condenser 11 to fall below a predetermined value required for proper operation of expansion valve l8. Under the latter circumstances, it is necessary to raise the pressure within condenser 11 to cause thermal expansion valve 18 to operate properly.

In accordance with the present invention, a control arrangement is provided for performing a plurality of combined functions including the raising of the pressure of refrigerant within condenser 11. This control arrangement includes a conduit 25 in communication with conduit 12 leading from the outlet of compressor 10, conduit 25 being in communication with pressure controlled valve 26, which in turn, is in communication with the nozzle 36' of ejector 16 via conduit 27. When the refrigeration system is operating in its above described normal manner, the pressure at the outlet portion 28 of ejector 16 is at a predetermined value and this pressure is communicated to valve 26 through conduit 29. Under the foregoing circumstances, valve 26 will be closed.

However, in the event that the pressure of condenser 11, resulting from its being cooled by low temperature ambient air, falls below the minimum predetermined value required for satisfactory operation of thermal expansion valve 13, the pressure in outlet portion 28 of ejector 16 will also fall and this reduced pressure will be imposed upon valve 26 via conduit 29, thereby causing valve 26 to open. The opening of valve 26 permits hot gases produced by compressor 1% to flow into the nozzle 36 of ejector 16 and these hot gases are mixed with liquid refrigerant entering ejector chamber 31 from conduit 14 leading from condenser ill. The mixing of gaseous and liquid refrigerant in the foregoing manner raises the pressure of refrigerant in condenser 11 by retarding flow of liquid refrigerant therefrom thereby causing liquid refrigerant to hang up therein and effectively block oif a portion of the condensing surface of condenser 11. The

entry of heated gaseous refrigerant into chamber 31 of ejector 16 causes an increase of refrigerant pressure in receiver 17, this increase in pressure assisting in the flow of refrigerant through thermal expansion valve 18. By blocking off a portion of the condenser surface, the pressure of refrigerant is raised above the predetermined minimum value necessary for proper operation of thermal expansion valve 18.

However, a condition may be reached, especially at the start up of a conventional refrigeration system, wherein too much liquid will hang up within condenser 11 and thereby cause the compressor It to cycle to an oif condition because the maximum permissible compressor pressure will be exceeded. As can be seen from the drawing, compressor 19 will remain in operation when a circuit is completed from line L1 through lead 32, on-off switch 33, lead 34, compressor 10, lead 35, pressure controlled switch 36, and lead 37 to line L2. As long as the compressor pressure remains below the above-mentioned predetermined maximum value, the foregoing circuit will cause compressor 1% to operate, assuming that other controls in the circuit (not shown) show a need for refrigeration system operation. In the event that the pressure of gases being supplied to conduit 12 by compressor 10 should exceed said predetermined maximum value because of excessive blocking of the condenser by liquid refrigerant, bellows 38 will expand because the latter is in communication with compressor outlet conduit 12 through conduit 39. The expansion of bellows 38 will cause switch 36 to open, breaking the electrical circuit to compressor 10 and causing the latter to shut off. As soon as the pressure in conduit 12 leading from compressor 10 is reduced, switch 36 will again close to cause the compressor to turn 011. This alternate opening and closing of switch 36 causes undesirable cycling of the compressor. This cycling action of the compressor is obviated by the present invention because whenever the pressure in conduit 12 leading from compressor 10 increases, the flow of gases through conduit 25, valve 26 and conduit 27 into nozzle 30 of ejector 16 will also increase and thereby cause the ejector 16 to assume an inducing function whereby it drains liquid refrigerant from condenser 11 at a relatively great rate thus reducing the pressure of gases in conduit 12 and eliminating cycling of compressor 10.

One function of ejector 16 of the present invention is to act as a conduit for conducting refrigerant from the condenser to the thermal expansion valve under a first set of conditions, namely, when the ambient air temperature utilized for cooling the ejector is within a predetermined range of values sufiicient to provide proper operation of the thermal expansion valve. A second function of ejector 16 is to act as a mixing chamber to mix gases leaving compressor 10 with liquid leaving condenser 11 to thereby raise the condenser pressure to a value sufilcient to effect proper flow of refrigerant through the circuit by causing the hang up of refrigerant in said condenser when the ambient air temperature utilized for cooling said condenser causes the condenser pressure to fall below a predetermined minimum value. A third function of ejector 16 is to act as a pump to drain liquid from condenser 11 when a sufficient amount of liquid collects therein to raise the pressure of gases leaving compressor 10 to a value which would normally cause the compressor to shut off.

If desired, a valve 40 may be placed in parallel across valve 26 by means of bypass conduits 41 and 42, the former being in communication with conduit 25 and the latter being in communication with conduit 27. Valve 49 is utilized when additional compressor capacity is added to the system and this valve may be manually controlled or automatically controlled, its purpose being to permit more gaseous refrigerant to pass to nozzle 30 of ejector 16 whenever additional compressor capacity is utilized.

While the valve 26 is shown as being controlled from the outlet 28 of ejector 16, it will be understood that any other control point in the refrigeration system may be utilized for controlling the opening and closing of valve 26. These control points may be either temperature or pressure responsive, as desired. Valve 26 may be of the type which is either on-or-off, or of the type which modulates in accordance with the pressure at the outlet of the ejector.

In FIGURE 2, I have disclosed a modified form of the invention in which the receiver 17' is dead-ended and is provided with suit-able supplemental heating mechanism such as a coil 50 which may be placed in or adjacent receiver 17'. As shown, compressed gaseous refrigerant is forwarded from the compressor through line 12 to condenser 11, refrigerant passing from condenser 11 through line 14 to ejector 16. Refrigerant from ejector 16 passes into line 51, receiver 17' and line 19 being connected to line 51.

Valve 26 is provided in conduits 25, 27 and is actuated in response to the pressure at the outlet portion 28 of ejector 16, as previously described. Valve 40 is placed in parallel across valve 26 by means of bypass conduits 41, 42. Valve 40' may be controlled by compressor discharge pressure or from the compressor capacity control, if such be employed in the system.

In the embodiment shown in FIGURE 2, ejector 16 serves as a mixer for the by-passed hot gas and liquid refrigerant from condenser 11 at low outdoor ambient temperature when the system has relatively little capacity change. By the use of valve 40 in combination with ejector 16, it is possible to remove refrigerant liquid rapidly from the condenser and the receiver and prevent high head pressure cycling when compressor capacity is added. It will be understood that during summer or high outdoor ambient conditions, valves 26, 40' are closed and do not affect system operation.

While a preferred embodiment of the present invention has been disclosed, it will be readily understood that the present invention is not limited thereto, but may be otherwise embodied within the scope of the following claims.

I claim:

1. A refrigeration system comprising a compressor, a condenser, expansion means, an evaporator, an ejector interposed between said condenser and said expansion means, said ejector having a nozzle and an inlet, said ejector receiving liquid refrigerant through said inlet and functioning as a conduit to pass liquid refrigerant from said condenser to said expansion means when said condenser pressure is above a predetermined minimum value, conduit means coupling the outlet of said compressor to the nozzle of the ejector, valve means in said conduit means, control means for opening said valve means when condenser pressure falls below said predetermined minimum value whereby gaseous refrigerant-from said compressor passes to the nozzle of the ejector and is mixed with liquid refrigerant passing to the ejector inlet from said condenser thereby causing liquid refrigerant to block a portion :of said condenser and raising the pressure of refrigerant in said condenser above said predetermined minimum value, compressor cutout means operatively associated with said compressor for shutting off said compressor when the pressure produced thereby exceeds a predetermined maximum value, the raising of the condenser pressure causing an increased flow through said conduit means to the nozzle of the ejector causing liquid refrigerant to be induced from said condenser tending to reduce the pressure produced by said compressor before said cutout means experiences a condenser pressure in excess ofsaid predetermined maximum value, whereby said ejector acts both to raise condenser pressure and to prevent said compressor pressure from exceeding said predetermined maximum value thereby preventing said compressor cut-out means from shutting off said compressor.

2. A refrigeration system as set forth in claim 1 including a receiver operatively interposed between said ejector and said expansion means.

3. A refrigeration system as set forth in claim 1 including second conduit means for effecting communication between said ejector and said valve means thereby controlling the operation of said valve means in response to the pressure at said ejector.

4. A refrigeration system comprising a compressor, a condenser, expansion means, and an evaporator connected in series circuit relationship, an ejector having an inlet, an outlet, and a nozzle, first conduit means for effecting communication between an outlet portion of said condenser and said inlet of said ejector, means for effecting communication between the outlet of the ejector and the expansion means, and second conduit means for effecting communication between said compressor outlet and said nozzle of said ejector whereby the flow of refrigerant from said compressor through said nozzle causes said ejector to induce refrigerant from said condenser.

5. In a refrigeration system, the combination of a compressor, a condenser, expansion means and an evaporator connected in series circuit relationship, first means for shutting off said compressor when the pressure produced thereby exceeds a predetermined maximum value, and second means operatively coupled between the outlet of said compressor and an outlet portion of said condenser for causing flow of refrigerant from said compressor directly to said condenser when the condenser pressure is above a predetermined minimum value sufficient for proper operation of said expansion means, for causing mixing of gaseous refrigerant leaving said compressor with liquid refrigerant leaving said condenser when said condenser pressure is below said predetermined minimum value retarding flow of liquid refrigerant from said condenser thereby raising the condenser pressure above said predetermined minimum value required for providing proper operation of said expansion means, and for inducing liquid from said condenser when liquid refrigerant blocks said condenser to too great a degree and the pressure produced by said compressor tends to rise above said predetermined maximum value which will cause said compressor to shut off, the inducement of liquid from said condenser substantially eliminating cycling of said compressor by preventing the exceeding of said predetermined maximum compressor pressure, said second means including an ejector having a liquid inlet and a nozzle, first conduit means for coupling the outlet of the compressor to said nozzle, second conduit means for coupling said outlet portion of the condenser to the liquid inlet of said ejector, and control means responsive to a condition of the refrigeration system for selectively controlling the operation thereof.

6. A refrigeration system in accordance with claim 5 in which the control means include valve means in said first conduit means and means coupling said valve means to said ejector thereby controlling the operation of said valve means in response to pressure conditions in said ejector.

References Cited in the file of this patent UNITED STATES PATENTS 

4. A REFRIGERATION SYSTEM COMPRISING A COMPRESSOR, A CONDENSER, EXPANSION MEANS, AND AN EVAPORATOR CONNECTED IN SERIES CIRCUIT RELATIONSHIP, AN EJECTOR HAVING AN INLET, AN OUTLET, AND A NOZZLE, FIRST CONDUIT MEANS FOR EFFECTING COMMUNICATION BETWEEN AN OUTLET PORTION OF SAID CONDENSER AND SAID INLET OF SAID EJECTOR, MEANS FOR EFFECTING COMMUNICATION BETWEEN THE OUTLET OF THE EJECTOR AND THE EXPANSION MEANS, AND SECOND CONDUIT MEANS FOR EFFECTING COMMUNICATION BETWEEN SAID COMPRESSOR OUTLET AND SAID NOZZLE OF SAID EJECTOR WHEREBY THE FLOW OF REFRIGERANT FROM SAID COMPRESSOR THROUGH SAID NOZZLE CAUSES SAID EJECTOR TO INDUCE REFRIGERANT FROM SAID CONDENSER. 